farnham



(No Model.) 3 Sheets-Sheet 1.

I. H. FARNHAM.

TELEPHONE APPARATUS.

No. 373,519. Patented Nov. 22, 1887. K

fnv/enor.

N. PETERS, PholoLillgogr-nphor, Wm; n nnnnnn c.

(No Model.) 3 SheetsSheet 2.

I. H. PARNHAM.

TELEPHONE APPARATUS.

No. 373,519. Patented Nov. 22, 1887.

Wi'messes.

Invenjan u PUERS. Phmo-Litlugnpban Wnhinglun, n. c,

(No Model.) 3 Sheets-Sheet 3.

I. 'H. FARNHAM.

TELEPHONE APPARATUS.

No. 373,519. Patented Nov. 22, 1887.

Wzlneaaea Imam 0602? UNITED STATES PATENT ISAIAH H. FARNHAM, OF MALDEN, MASSACHUSETTS, ASSIGNOE TO THE NEWV ENGLAND TELEPHONE COMPANY, OF NEYV YORK, N. Y.

TELEPHONE APPARATUS.

SPECIFICATION forming part of Letters Patent No. 373,519, dated November 22, 1887.

Application filed April '2, 1887.

To all whom it may concern.-

Be it known that I, ISAIAH H. FARNHAM, of Maiden, in the county of Middlesex and State of Massachusetts, have invented certain Improvements in Telephone Apparatus, of which the following is a specification.

My invention relates to the arrangement of elect-r0 magnetic annunciators of the class chiefly utilized as call-receiving and disconmeeting-signal appliances for telephone-circuits. Its object is to provide a practical means of obtaining a signal at a telephone central station from either of two lines interconnected at said station for through communication, which, when used, shall not be subject to the draw-backs and inconveniences usually experiencedwhcn electromagnetic helices are included in speaking-telephone circuits while speech is being transmitted.

In telephony it has been found that when electro-magnets areincluded in the circuit the telephonic currents are opposed and rendered sluggish and comparatively inefficient to a greater degree than can possibly be due to the 2 more electrical resistance of the circuit and the instrument-helices, and it has further been demonstrated that the inefficiency is due to a partial neutralization effected by counter-currents generated in the several electromagnetic 3o helices under the influence of the magnetic variations of the iron cores thereof, which variations are primarily caused by the passage through the said helices ofthe constantly-varying voice-currents which traverse the main 5 circuit. Even in comparatively short lines this adverse influence is plainly perceptible, and its ultimate efi'ect is to diminish the strength and volume of the legitimate or voice currents, and consequently to produce a dis- 40 torted and confused effect in the reproduced sounds together with a pronounced attenuation of the said sounds. \Vhen, however, the te1ephone-lines are of great length, (as, for example,when the local lines of two central stations at a distance from one another are united by trunk or interurban lines,) the opposing currents due to the magnetic reaction exercise a greatly-intensified influence upon the line and render the main current so sluggish as to diminish very seriously the distinctness of the reproduced articulate sounds and to run the Serial No. 233,349. (No modcll) words very much together; nor is this trouble exclusively restricted to helices having iron cores in them. In a less degree it is notice able in helices which do not surround iron, and is of course due to the extra current produced by the self-induction of each convolution on the others; and inasmuch as the electro-motive force of such disturbing currents depends, other conditions being considered, upon the number of the convolutions in the helix, it follows that the adverse effects are very much plainer and more disastrous in their results when magnets or coils of fine wire and many convolutions of the same are employed. 55 It has, however, heretofore been regarded as essential to use magnets of high resistance, this of course implying agreat number of convolutions on account of the very considerable mechanical inertiapossessed by the ordinary 7o telephonic appliances, and by reason of the com paratively energetic electromagnetic force required to overcome such inertia. Moreover, since it is essential in the operation of telephone-lines that they shall be disconnected as soon as possible after the discontinuance of a conversation, it is-considcred impracticable to dispense with the use of intervening annunciatorniagnets in some form which are required to give a disconnecting-signal.

By the use of my invention the evils stated hereinbefore are materially ameliorated; and it consists in combining, with the main line interconnecting devices and call-receiving annunciators, a normally-open local circuit in- 85 eluding a source of electricity and a relay of extremely low resistance, either permanently included in the said main line or brought into contact therewith only when two lines are united for intercommunicatio-n, the said relay 0 being adapted to attract a light and easilymoving armature acting as a circuit-closer for the said local circuit, which when closed is adapted to operate the call-receiving annunciator, the latter being common both to the 5 main line and to the normally-open local circuit, being in circuit normally with the former and adapted then to indicate the subscribers call, but being disconnected therefrom by the act of connecting two lines, and I00 thereupon adapted to respond to the closing of the normally-open local circuit only when the said two lines are connected, whereby it is enabled to serve as a disconnecting-signal without the inconveniences attending its permanent inclusion in the main line for that purpose.

A special annunciator may be used in a local circuit, or I may use the line-calling annunciator, and the current operating it may be derived from a battery or from a magneto electric machine or other source of dynamic electricity.

It is usual to employ in disconnecting-signals annunciator magnets the coils of which measure from fifty to seventy-five ohms resist ance; and ordinarily a magnet of'less resistance cannot be considered trustworthy for the purpose of releasing the disconnecting-signals of long lines. In the use of my invention, however, I find in practice that though an electro-maguet of extremely low resistance cannot be relied upon to do' the comparatively heavy mechanical work of releasing an an nunciator, such a one having a resistance even less than four ohms will suffice to actuated delicately suspended relay-armature which will operate asa circuit-closer, and thereby to change the condition of a local circuit, evei1 when the main lines are seventy-five miles in length. I prefer, generally, to use an electro magnet having a resistance of about five ohms wound with wire about .015 inch diameter. Y

In the drawings which form a portion ofthis specification, Figure 1 is a sectional elevation of a telephone switch-board, showing the application of my invention. Figs. 2, 3', an'd4 are diagrams showing modifications in arranging the electrical circuits therefor, and Fig. 5 is a diagram showing the application of a singlelocal battery to a number of disconnecting relays.

Referring first to Fig. 1, A represents the vertical part of a telephone switch-board of usual form upon which lines are connected together, and B is the horizontal table thereof, at which such connections are supervised and provided with the ordinary operators outfit. The entering lines 7 8 9, 850., enter from telephone sub-stations D E, &c., and pass each first to the spring3 oftheirrespectiv'e spring-jacks 2, thence normally to the insulated contactpins 4, and by wires 5 to their regular call-arinunciators, after passing which each line terminates in an earth-wire, 11, leading to earth at G.

When any two lines are to be united for intercommunication, this is effected bymeans of two connecting pins or plugs,1 and 6, through their connecting-cords'c' and c andtheproper intervening appliances. The plugs 1 and 6 are inserted in the spring-jacks 2 and raise the springs 3 from their respective contacts 4,

'thus transferring the path ofthe line from the said contacts to a new route through the said plugs l and 6 and their flexible conduc'tdrs.

Although not forming apart of my invention, I will for elearness of description trace the route of the circuit from plug to plug.

flexible conductor 0 to spring-key 10,which is mounted on a non-conducting block,32,and is controlled wit-h reference to its forward and back contacts by the pressbutton p thence, when the said key is not pressed, to back-coutact 27, wire 26, cam-spring 20, spindle end 18, cam-spring 22, and wire 13, to the lowresistance magnet e; thence by wire 14 to binding-screw 3, flexible conductor a, and plug 6, which is'inserted in the spring-jack of line No. 9. The lines 8 and 9 are thus united through the low-resistance magnet e. The lower contact,28, of key 10 is insulated, and serves as the terminal of a wire, 29, leading to a generator, 0, so that by pressing thebutton p call-signals can be sent to line.

The telephones T can be introduced into the u'nitin'g loop by changing the position of the cam-lever 15. The cam 16 is thus moved round, and allows its spindle 17 to rise under with the lines 8 and 9. The two cords a and c are kept taut and normally retracted and in position in their seats on the table B by means of the weights to, which also keep the buttends of the plugs (which are themselves c'oirductors and in connection with the c'ondiieting ends) in contact with the earth-plate 3 l ,united to earth by wire 30.

The interposed electro-magnet e, which is,- as hereinbefore stated, of low resistance, is mounted in a suitable position in the frame A, and is provided with an armature, 1', delicately suspended from a non conducting block; 9, by a light spring, 8, (or in trunnions; ifpreferred.) This armature rests normally on its backliuiit-stop h. The armature is electrically united by a wire, 34, with one pole of a local battery, b, and from its front stop, 73, a wire; 35, leads to one terminal of the annunciator; magnetf, while from the remaining terminal of the said magnet a wire, 33, extends to the other pole of the local battery 6. The suspending spring 3 gives sufficient retractile force to the armature to keep it normally in its back position, and its normal position and length of stroke are regulated by the adjustable screw h. The annunciator-magnetf, which may be of any suitable resistance, is thus cludod in a local-battery circuit,normally open at the armature contact-point i, and controlled by the low-resistance relay-magnet e. The magnet 6', therefore, alone is included in the circuit of the united telephone-lines, and its armature and front contact act together to constitute a circuit-closer for the local circuit.

Figs. 2, 3, and 4 are diagrams illustrating, severally, modifications in arrangement.

In Fig. 2 the incoming line 8 passes first through the spring -jack j, mounted in the switch-board frame A, and proceeds by wire 42 through its regular calling-annnnciatorf and wire 43 to earth. In this case the annunciator, being in the line circuit and of the ordinary form, would be of the usual resistance; but from the point x in the normal circuit of the main line a wire, 44, extends to the front contact of the relay-armature g. The relay e, as in Fig. 1, is in the circuit of the connectingcords 45 and 46 and the plugs 2, and is thus adapted to form a part of the temporary circuit made by uniting two lines together. \Vhen either plug is inserted in the spring-jack j, the spring of said jack is lifted from its contact 4 and rests upon the plug end. The wire 42 then terminates and is open at the end of said contact 4; but by virtue of. the branch line 44, whichediverges from the cut-off portion 42 of the mainline, the same annunciator f, which originally, through its insulated pin 4, was included in the main line to constitute the callingsignal, is now in a normally-open local circuit which includes the battery I), so that when the disconnecting-signal is sent and the armature g attracted by the relay-magnet e the local circuit comprising battery I) and annunciatorf is closed at the point 35, and the annunciator gives the said disconnecting-signa Fig. 3 differs from the foregoing examples only in that the relay e is permanently in the main circuit in addition to the annunciatorf, and in consequence is not needed in the connecting-cord loop.

In Fig. 5 I show a modification in which the low'resistance relay 0 is included in the main line 9, (either permanently or by means of connecting-cords,) which relay has its armature g hung in trunuions g. A battery, I), of the type known as closed-circuit batteries is maintained on closed circuit, its leading wires m and a being connected with the annunciator f, which is thus in the batterycircuit. The annunciator is, however, shunted by the wires 0 and u, the armature g, and its backcontact, h, so that the major part of the battery-current passes through the shunt. \Vhen the arma ture is attracted by its electro-magnet, the latter being energized by the electric currents of the signal to disconnect, the shunt-circuit is broken and the aununciatormagnet receiving the entire battery-current is made operative, and the said disconneetingsignal is thereupon received.

In Fig. 4 I show that a number of the dis- I connecting annunciators can be operated through their respective relays by the same battery or source of electricity.

I do not broadly claim the use of a relay-and local circuit in a telephone disconnecting signal, since I am well aware that such an organization is old in the art; nor do I claim a relay in a telephone-circuit when the said relay is of an ordinarily high resistance, as where heretofore relays have been used they have been of as great or greater resistance than is necessary in direct-working an'nunciators, and it is this resistance and the counter-currents which are in a great measure dependent thereon.

I claim- 1. A main telephone-line, a normally-open local circuit, a call-annunciator common to both circuits and included in the main line between the spring-jack and the earth-terminal, a relay of low resistance, also included or adapted to be included in said main line at a point external to said annunciator, and a sensitive circuit-closer operated by said relay and acting to close the local circuit, substantially as and for the purposes specified.

2. A main telephone'circuit extending at a central station through a spring-jack or connecting device and an annunciator to earth, a normally-open local circuit including a suit able source of electricity, a circuit-closer, and the terminal portion of the main line, together with the said annunciator, means, asindicated, for connecting any two lines together through the spring-jacks thereof and for disconnecting their respective normal earth-terminals, and a low'resistance relay included in the compound circtiitthus formed and adapted to act uate the circuit-closer to close the local circuit thereby, and to operate the annunciator, whereby the main-line calling-annunciator may also be utilized in the local circuit as a disconnecting-signal.

3. The combination ofa telephone main-line circuit provided at its terminal station with a spring-jack or plug-socket'circuit-changer, and a call-receiving annunciator, the latter being nearer to the earth-terminal than the former, a connectinglink for uniting the said main circuit With any other like main circuit, the said link consisting of a flexible conductor terminated at each end by a plug-connector and including a relay, and a normally-open branch circuit extending from a point upon the main circuit between the spring-jack and the annuneiator to the front contact-stop of the relay-armature, whereby when the plug-connector is inserted in the said spring-jack the said annunciator is withdrawn from the main circuit and caused to form a part of a normallyopen local circuit including the said branch of the main line, the relayarmature, and a source of electricity, and controlled by the said relay, substantially as described.

In testimony whereof Ihave signed my name to this specification, in the presence of two subscribing witnesses, this 25th day of March, 1887.

ISAIAH H. FARNHAM.

W'itnesses:

THOS. D. LOOKWOOD, Gno. WILLIs PIERCE. 

